System and method for multi-tier synchronization

ABSTRACT

The present invention provides a system and method for multi-tiered data synchronization. Data is synchronized between a master synchronization server, one or more proxy synchronization servers, and client devices. Client devices establish synchronization sessions with either a proxy synchronization server or a master synchronization server, depending on which server provides the “best” available connection to that client device. Each proxy synchronization server synchronizes data with client devices that have established a synchronization session with such proxy synchronization server. The master synchronization server synchronizes data with client devices that have established a synchronization session with the master synchronization server. Each proxy synchronization server synchronizes data with the master synchronization server. Metadata associated with synchronized files is synchronized throughout the system in real-time. Files may be synchronized in real-time or at a delayed time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 12/383,693 entitled “System and Method for Multi-Tier Synchronization” and filed on Mar. 26, 2009, and claims priority to Application No. 61/072,008, entitled “System and Method for Multi-tier Synchronization” filed on Mar. 27, 2008, each of which is expressly incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates generally to synchronization/back-up server systems, and more, specifically, to a method for multi-tier synchronization.

2. Description of the Background Art

Real-time synchronization systems, including client-server solutions such as MICROSOFT EXCHANGE (email/PIM) and SHARPCAST's first photo synchronization system, only synchronize data between a client and a server, where the client communicates with the server via the Internet. The advantage of client/server synchronization over the Internet is that the client device can access the server anytime it has an Internet connection. Also, by storing files on the server, the files can be easily recovered should the files on the client device be lost. There are at least two disadvantages with client/server synchronization over the Internet. Transferring files over the Internet is slower than transferring files over a local area network or an Intranet. Also, if a master server stores all synchronized files from many client devices, the master server has to have very large storage capabilities, which can be quite expensive.

An example of master server-client synchronization is described in U.S. patent application Ser. No. 11/269,498 titled “Method and Apparatus for a File Sharing and Synchronization System,” and filed on Nov. 8, 2005 with first-named inventor Jack B. Strong, the contents of which are incorporated by reference as if fully disclosed herein.

Known multi-tier data management systems, such as web proxies, content delivery networks, or file replication technologies, such as “rsync,” distribute file storage over the network. This means that client devices can retrieve files from intermediate sources instead of downloading then from a master server. Such intermediate sources may be connected to client devices over a local area network, where file transfers typically occur at a faster rate that transfers over the Internet. A disadvantage with known multi-tier data management systems is that data is not synchronized in real-time, which comprises user experience.

It would be desirable to have a synchronization system that was able to take advantage of the best of both multi-tier data management and client-server synchronization.

SUMMARY

The present invention provides a system and method for multi-tiered data synchronization. Data is synchronized between a master synchronization server, one or more proxy synchronization servers, and client devices.

Client devices establish synchronization sessions with either a proxy synchronization server or a master synchronization server, depending on which server provides the “best” available connection to that client device. “Best” means fastest, cheapest, or more secure, as per the client device's requirements. In one embodiment, client devices that can communicate with a proxy synchronization server over a local area network or intranet establish synchronization sessions with the proxy synchronization server instead of the master synchronization server.

Each proxy synchronization server synchronizes data with client devices “connected” to it (i.e., client devices that have established a synchronization session with the proxy synchronization server). The master synchronization server synchronizes data with client devices connected to it (i.e., client devices that have established a synchronization session with the master synchronization server via the Internet). Each proxy synchronization server synchronizes data with the master synchronization server.

In the preferred embodiment, metadata associated with synchronized files or data objects is synchronized throughout the system in real-time. Files may be synchronized in real-time or at a delayed time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that illustrates an example of a synchronization system.

FIG. 2 illustrates a method for multi-tier synchronization.

FIG. 3 illustrates an example of multi-tier synchronization.

FIG. 4 illustrates another example of multi-tier synchronization.

FIG. 5 illustrates a further example of multi-tier synchronization.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a system and method for multi-tiered data synchronization. Data is synchronized between a “master” synchronization server, one or more “proxy” synchronization servers, and client devices. FIG. 1 is an example of a system 100 that includes a master synchronization server 60, a proxy synchronization server 30, and client devices 10, 20, 25, 40, and 50.

Master synchronization servers may, for example, be servers that are hosted in a data center and that are accessible via the Internet. Proxy synchronization servers may, for example, be included with Network Attached Storage (NAS) devices found in homes and offices, in media center or set top box systems found in home networks, in broadband routers found in home networks, and in dedicated appliances found in offices and home offices. Types of client devices include personal computers, mobile phones, PDAs, and other networked devices.

FIG. 2 illustrates a method for multi-tiered data synchronization in a system that includes a master synchronization server, one or more proxy synchronization servers, and a plurality of client devices. Client devices establish synchronization sessions with either a proxy synchronization server or a master synchronization server, depending on which server provides the “best” available connection to that client device (step 210). “Best” means fastest, cheapest, or more secure, as per the client device's requirements.

In the preferred embodiment, client devices that can communicate with a proxy synchronization server over a local area network or intranet (“local client devices”) establish synchronization sessions with the proxy synchronization server instead of the master synchronization server. Online client devices that are unable to communicate with the proxy synchronization server via a local area network or intranet (“remote client devices”) establish synchronization sessions with a master synchronization server.

Consider for example, client device 10 in FIG. 1. Client device 10 could connect over the Internet to the master synchronization server, with a connection speed of several megabits per second, or it could connect to the proxy synchronization server 30 over the local area network 15 with a connection speed to up to, a gigabit per second. Client device 10 would likely choose to connect to the proxy synchronization server 30. If client 10 is a mobile device that is taken to another location, it may no longer be able to connect to the proxy synchronization server 30 (for example, because the proxy synchronization server 30 is behind a firewall and is not accessible outside the user's home network). In this case, client device 10 would connect directly to the master server 60 via the Internet. In FIG. 1, client devices 40 and 50 are outside the local area network 15, and, thus, would establish synchronization sessions directly with the master synchronization server 60.

Referring again to FIG. 2, data is synchronized between the master synchronization server, the proxy synchronization server(s), and client devices (step 220). Each proxy synchronization server synchronizes data with client devices “connected” to it (i.e., client devices that have established a synchronization session with the proxy synchronization server, usually over a local network) (step 230). The master synchronization server synchronizes data with client devices connected to it (i.e., client devices that have established a synchronization session with the master synchronization server via the Internet) (step 240). Each proxy synchronization server synchronizes data with the master synchronization server (step 250).

Metadata associated with synchronized files is synchronized throughout the system in real-time. The master synchronization server stores all metadata associated with synchronized files/data objects in the system. Each client device and proxy synchronization server stores all metadata relevant to such device. Copies of synchronized files/data objects may be transferred along with the metadata or may be retrieved “on demand.” The master server and the client devices may or may not store actual copies of synchronized files. However, in one embodiment, all files are backed up on to one or more of the proxy synchronization servers. In the preferred embodiment, files are synchronized in real-time between the proxy synchronization servers and interest client devices connected to it (i.e., client devices that have established a synchronization session with the proxy synchronization server). Similarly, in such embodiment, files are synchronized in real-time between the master synchronization server and interested client devices connected to it. Files may be synchronized between the master synchronization server and each proxy synchronization server either in real time or at a delayed time. In one embodiment, two devices (where client devices or a server) that have established a synchronization session between themselves maintain a dedicated connection to each other throughout the synchronization session, thereby enabling data (e.g., metadata, files, data objects) to be synchronized in real time.

FIG. 3 illustrates an example multi-tier synchronization scenario with respect to the system 100 illustrated in FIG. 1. In this example, client devices 10, 20, and 25 have each established a synchronization session with proxy synchronization server 30 via local area network 15, and client devices 40 and 50 have each established a synchronization session with master synchronization server 60 via the Internet. In the example, a file is created or edited on client device 10 (step 310). Client device 10 synchronizes the file and associated metadata with proxy synchronization server 30, which stores a back up copy of the file (step 320). The proxy synchronization server 30 synchronizes the metadata, and optionally the file, with master synchronization server 60 and interest client devices that are connected to the proxy synchronization server 30 (i.e., client device 20, 25) (step 330). The master synchronization server 60 then synchronizes the metadata, and optionally the file, with interest client devices connected to the master synchronization server 60 via the Internet (i.e., client devices 40, 50) (step 340). Metadata is preferably synchronized throughout the system 100 in real-time. Files can be synchronized in real time or at a delayed time.

FIG. 4 illustrates another example scenario, in which a file is created or edited on client device 40 (step 410). The client device 40 synchronizes the file and associated metadata with master synchronization server 60 via the Internet (step 420). The master synchronization server 60 synchronizes the metadata, and optionally the file, with interested client devices that have established a synchronization session with the master synchronization server (i.e., client device 50) (step 430). The master synchronization server also synchronizes the file and metadata with the proxy synchronization server 30 (step 440), and the proxy synchronization server 30 synchronizes the metadata, and optionally the file, with interested client devices that have established synchronization sessions with the proxy synchronization server 30 (i.e., client devices 10, 20, 25) (step 450). As discussed in more detail below, the master synchronization server may store a copy of file, or it may simply pass the file on to the proxy synchronization server 30, which stores a back up copy of the file. Metadata is preferably synchronized throughout the system 100 in real time. Files may be synchronized in real-time or at a delayed time.

FIG. 5 illustrates another example scenario with respect to the system 100 illustrated in FIG. 1. In this example, a file is created or edited on master server 60 via a web interface (step 510). The master synchronization server 60 synchronizes the metadata, and optionally the file, with interested client devices that have established a synchronization session with the master synchronization server 60 (i.e., client devices 40 and 50) (step 520). The master synchronization server 60 also synchronizes the file and metadata with the proxy synchronization server 30 (step 530), and the proxy synchronization server 30 synchronizes the metadata, and optionally the file, with interested client devices that have established synchronization sessions with the proxy synchronization server 30 (i.e., client devices 10, 20, 25) (step 540). As discussed in more detail below, the master synchronization server may store a copy of file, or it may simply pass the file on to the proxy synchronization server 30, which stores a back up copy of the file. Metadata is preferably synchronized throughout the system 100 in real time. Files may be synchronized in real-time or at a delayed time.

The multi-tiered synchronization method of the present invention can be used to more effectively utilize network bandwidth than traditional client-server architectures. Multi-tier synchronization can be configured to utilize less bandwidth over the Internet during peak usage hours, when that connection may be in high demand by other applications. For example, a client device may synchronize a new file to a proxy synchronization server. This transfer may happen at a high bitrate, as it is likely over a local area network, or high speed intranet. The proxy synchronization server makes this file immediately available to other client devices connected to the proxy synchronization server. The file is backed up on the proxy synchronization server, and, thus, if the client device's hard disk fails, the file can be restored from the proxy. However, the proxy synchronization server need not synchronize the file to the master synchronization server immediately. It could defer syncing the file until the Internet connection (which is often slower and more contentious than the connection from the local client devices to the proxy synchronization server) until an idle period (e.g., the middle of the night). Alternately, the proxy synchronization server may sync files with the master synchronization server throughout the day, but only use a low percentage of Internet bandwidth while other applications require bandwidth, and a high percentage when the Internet connection is idle. Despite this variable bandwidth synchronization to the master synchronization server over the Internet, the proxy synchronization server is able to synchronize files at a high speed to client devices connected to the proxy synchronization server.

In the preferred embodiment, metadata is synchronized in real-time, even if files may are synchronized on a deferred schedule. Since metadata takes very little bandwidth to synchronize, metadata changes can be synchronized up from the proxy synchronization server to the master synchronization server in real time, providing all clients with up-to-date metadata. This can, for example, prevent clients from making conflicting changes to a file even if that file has not been synchronized to the master synchronization server (pending an idle period), since the file's revision information can be described in metadata.

In one embodiment, conflict resolution is employed hierarchically. A conflict resolution algorithm can be applied on the proxy synchronization server when conflicting changes are synced to it, or on the master synchronization server when receiving conflicting changes from any combination of proxies or directly connected clients.

File storage requirements on the master synchronization server may be minimized by relying on proxy synchronization servers to back up files. In one embodiment, the master synchronization server stores only metadata and no files. In an alternate embodiment, the master synchronization server stores only select files. For example, the proxy synchronization server could store all versions of a file, and the master synchronization server could store only the most recent version of a file. As another example, the master synchronization server could store only files having a specific tag or rating (music files rated with 5 stars). As yet another example, the master synchronization server could store only files of a certain media type (e.g., photo files, music files).

In one embodiment, client devices will first attempt to synchronize with a proxy synchronization server if that option is available. If a proxy synchronization server is not available for synchronization, then, in such embodiment, the client device will synchronize with a peer client device if a peer client device is available for synchronization. If neither a proxy synchronization server nor a peer client device is available for synchronization, then the client device will synchronize with the master synchronization server. Peer-to-peer synchronization is described in U.S. patent application titled “Opportunistic Peer-to-Peer Synchronization in a Synchronization System” filed on Mar. 24, 2009 and having inventors Kiren R. Sekar and Jack B. Strong, the contents of which are incorporated herein by reference as if fully disclosed herein.

Examples of files include photos, music files, word processing documents, spreadsheets, slide presentations, and video files.

The methods disclosed herein can be used to synchronize data objects, such as email messages, text messages, contact items, and calendar items, in the same way that files are synchronized.

As will be understood by those familiar with the art, the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above disclosure of the present invention is intended to be illustrative and not limiting of the invention. 

The invention claimed is:
 1. A method for synchronizing metadata using a proxy synchronization server, the method comprising: supporting communication between a master synchronization server and a client device through the proxy synchronization server via synchronization sessions between the proxy synchronization server and the master synchronization server and between the proxy synchronization server and the client device; synchronizing the metadata during a first time, via the synchronization sessions, across the master synchronization server, the proxy synchronization server, and the client device in response to a change made to synchronized data on the client device with the metadata being associated with the change made to the synchronized data, wherein synchronizing the metadata comprises updating the metadata at the master synchronization server and the proxy synchronization server; and synchronizing the change made to the synchronized data during a second time, via synchronization sessions, across the master synchronization server, the proxy synchronization server, and the client device in response to the change made to the synchronized data on the client device, wherein the second time is later than the first time.
 2. The method of claim 1, further comprising: applying a conflict resolution algorithm on the proxy synchronization server when receiving conflicting changes to the metadata.
 3. The method of claim 1, wherein synchronizing the metadata during the first time occurs in real-time when a synchronization session between two or more devices is established.
 4. The method of claim 1, wherein, during the synchronizing of the metadata, the change made to the synchronized data is not synchronized on the master synchronization server, the proxy synchronization server, and the client device.
 5. The method of claim 1, further comprising: receiving, if the change to the synchronized data comprises a new file or an updated file on the client device, a file comprising a copy of the new file or the updated file from the client device; storing the file; and sending the file to an interested device that communicates with the proxy synchronization server.
 6. The method of claim 1, further comprising: backing up, on the proxy synchronization server, all synchronized data from the client device, wherein only specified synchronized data from the client device is backed up on the master synchronization server.
 7. The method of claim 6, wherein the backing up the synchronized data on by the proxy synchronization server further comprises: backing up, on the proxy synchronization server, all versions of the specified synchronized data, wherein only a latest version of the specified synchronized data is backed up to the master synchronization server.
 8. A non-transitory computer-readable medium comprising computer-executable code for synchronizing metadata using a proxy synchronization server, comprising: code for supporting communication between a master synchronization server and a client device through the proxy synchronization server via synchronization sessions between the proxy synchronization server and the master synchronization server and between the proxy synchronization server and the client device; code for synchronizing the metadata during a first time, via the synchronization sessions, across the master synchronization server, the proxy synchronization server, and the client device in response to a change made to synchronized data on the client device with the metadata being associated with the change made to the synchronized data, wherein synchronizing the metadata comprises updating the metadata at the master synchronization server and the proxy synchronization server; and code for synchronizing the change made to the synchronized data during a second time, via synchronization sessions, across the master synchronization server, the proxy synchronization server, and the client device in response to the change made to the synchronized data on the client device, wherein the second time is later than the first time.
 9. The non-transitory computer-readable medium of claim 8, further comprising: code for applying a conflict resolution algorithm on the proxy synchronization server when receiving conflicting changes to the metadata.
 10. The non-transitory computer-readable medium of claim 8, wherein synchronizing the metadata during the first time occurs in real-time when a synchronization session between two or more devices is established.
 11. The non-transitory computer-readable medium of claim 8, wherein the code for the synchronizing of the metadata further comprises: code for not synchronizing the change made to the synchronized data on the master synchronization server, the proxy synchronization server, and the client device.
 12. The non-transitory computer-readable medium of claim 8, further comprising: code for receiving, if the change to the synchronized data comprises a new file or an updated file on the client device, a file comprising a copy of the new file or the updated file from the client device; code for storing the file; and code for sending the file to an interested device that communicates with the proxy synchronization server.
 13. The non-transitory computer-readable medium of claim 8, further comprising: code for backing up, on the proxy synchronization server, all synchronized data from the client device, wherein only specified synchronized data from the client device is backed up on the master synchronization server.
 14. The non-transitory computer-readable medium of claim 13, wherein the code for backing up the synchronized data on by the proxy synchronization server further comprises: code for backing up, on the proxy synchronization server, all versions of the specified synchronized data, wherein only a latest version of the specified synchronized data is backed up to the master synchronization server.
 15. A proxy synchronization server configured to: support communication between a master synchronization server and a client device via synchronization sessions between the proxy synchronization server and the master synchronization server and between the proxy synchronization server and the client device; synchronize metadata during a first time, via the synchronization sessions, across the master synchronization server, the proxy synchronization server, and the client device in response to a change made to synchronized data on the client device with the metadata being associated with the change made to the synchronized data, wherein synchronizing the metadata comprises updating the metadata at the master synchronization server and the proxy synchronization server; and synchronize the change made to the synchronized data during a second time, via synchronization sessions, across the master synchronization server, the proxy synchronization server, and the client device in response to the change made to the synchronized data on the client device, wherein the second time is later than the first time.
 16. The proxy synchronization server of claim 15, wherein the proxy server is further configured to: apply a conflict resolution algorithm on the proxy synchronization server when receiving conflicting changes to the metadata.
 17. The proxy synchronization server of claim 15, wherein, during the synchronizing of the metadata, the change made to the synchronized data is not synchronized on the proxy synchronization server.
 18. The proxy synchronization server of claim 15, wherein the proxy synchronization server is further configured to: receive, if the change to the synchronized data comprises a new file or an updated file on the client device, a file comprising a copy of the new file or the updated file from the client device; store the file; and send the file to an interested device that communicates with the proxy synchronization server.
 19. The proxy synchronization server of claim 15, wherein the proxy synchronization server is further configured to: back up, on the proxy synchronization server, all synchronized data from the client device, wherein only specified synchronized data from the client device is backed up on the master synchronization server.
 20. The proxy synchronization server of claim 15, wherein the proxy synchronization server is further configured to: back up, on the proxy synchronization server, all versions of the specified synchronized data, wherein only a latest version of the specified synchronized data is backed up to the master synchronization server. 